The present invention relates to a bit for excavation and compaction equipment for erecting piles and to excavation equipment provided with said bit.
From the European patent No. EP 0 228 138 excavation and compaction equipment is known for erecting piles comprising a mast, a rotary table slidably mounted along the mast, a drill rod actuated by the rotary table, and a drill bit, which is mounted at a bottom end of the drill rod itself, and comprises, in turn, a central body having an outer diameter equal to an outer diameter of the rod, an excavation screw fixed to the central body, and a dislocating element arranged along the rod immediately above the screw for compaction of the walls of the excavation during drilling.
In the equipment of the type described above, the dislocating element comprises two closed screws with opposed geometry, which develop from one another around the central body in opposite winding directions, and have an initial outer profile equal to an outer diameter of the screw and an outer final profile tangential to the central body itself in such a way as to compact the soil during excavation.
As has been described also in the same patent referred to above, the equipment is subjected to a twisting moment on the drill rod and to a thrust on the excavation screw that are relatively high in so far as the mass of soil to be compacted during excavation by the dislocating element is considerable and also exerts a high resistance to advance of the bit in the earth itself. A stress of this sort entails construction of equipment of considerable dimensions and, furthermore, also calls for adequate driving power of the motors, which, however, is exploited only in the drilling stage, but not during extraction of the bit from the excavation and during filling thereof by injection of cement/concrete through the bit itself.